In the present program we plan to determine the structure and conformation by means of single crystal X-ray diffraction of the following type of molecules. We plan to study the structure and conformation and changes in conformation of a series of siderochromes and deferrsiderochromes in order to obtain a better understanding of the iron transport properties of these molecules through membranes in aerobiomicrobial organisms. Also the stereochemistry of the particular siderochromes will be determined. We plan to study nonplanar peptide bonds in a series of tri-and tetracyclic lactams and cyclic peptides, for which the results will be correlated with available IR data and theoretical studies. We hope to be able to prepare ternary complexes of Cu(II) peptide and simple aromatic molecules to study the possible interaction between Cu(II) and the aromatic molecule. Such an interaction previously observed, could well play a role in the mechanism of the copper oxidases. With the structure determinations of various chelates and complexes of peptides, with for instance Cu(II), Zn and Ca, we want to study the influence of these metals on the conformation of peptides at physiological pH. BIBLIOGRAPHIC REFERENCES: The Crystal and Molecular Structure of the Copper (II) Chelate of L-leucyl-L-tyrosine. D. van der Helm, S.E. Ealick and J.E. Burks. Acta Cryst. B31, 1013 (1975). The Crystal Structure of Trans Potassium N, N'-Ethylene bis (acetylacetoniminate) Diglycinato Cobaltate (III) Hexahydrate. S.R. Holbrook and D. van der Helm. Acta Cryst. B31, 1653 (1975).